I did my first oil change in my 05 last night...I drove the front tires on the ramps and let the fun begin

. About 2 or 3 minutes into it I heard this noise coming from the rear...it sounded like a small compresser and it only stayed on for like 15 seconds. So I went back to work and a few minutes later there it was again...it kept doing that throughout the oil change. If I didnt know any better I would have thought I had airbags that were trying to level the car out. Any one know what this noise was or expirience it themselves??? By the way, why would Jeep put the oil filter there

??? It was in a much better spot in my old 03 Lib.
Thanks for any thoughts...
~Bethany